Jacob M. "Jascha" Gegna or Gegner (Yiddish: יעקב געגנער, 1879–1944) was an American violinist, teacher, composer and recording artist.

Today he is mainly remembered for his work as a teacher in New York and Los Angeles, as well as his early twentieth century 78 rpm recordings of solo klezmer violin music which are among the only of their type to have been preserved.

Beilis' testimony during the trial made an impression on Jacob, who would later compose a violin piece in his honor.

[11] Jacob and his brother Max (Mischa) fled Russia at the outbreak of the First World War and emigrated to the United States, sailing from Antwerp and arriving in New York City in June 1914.

[11][25] In September 1924 he was honored by a 25th anniversary concert at Carnegie Hall; this featured his daughter Jenny (a soprano) and a number of his students, including Max Melti, Gabriel Engel, Helen de Witt Jacobs, Issay Lukashevsky, Olcott Vail and Benjamin Steinberg.

[7] After that he played a benefit concert for displaced Russian Jews; the event was headlined by Joseph Cherniavsky, who had recently arrived in the city and was presenting his "Chassidic Jazz Band" vaudeville act.

[9][32][33] In 1932 he was appointed head of the violin department at the Institute of Musical Education; the string orchestra he founded there debuted in 1933.

[34][35] In 1935 Jacob and Max's brother Naum, who had been living in Germany, emigrated to the United States and joined them in California.

[38] The original 78 disc of Taxim was also remastered and released on the 1999 reissue cd Oytsres: Klezmer music 1908-1996.